Now the question is if I submit "fm2", is it possible to also submit the text area which is in "fm1"? I don't want to repeat the same text area in both "fm1" and "fm2", so this text area can either submit to "fm1", or "fm2".

Well I didn't seen any direct way to do this, but you can use the, there may have a hidden field in fm2 for storing the value of textarea (fm1) and use this very very simple function to fill the value in hidden field.